4 Prof. E. Edluud on the Electrical 



the mercury had been carefully boiled, and the vacuum was 

 put into electric communication with the exterior by a plati- 

 num wire soldered to the glass in the upper extremity of the 

 tube*. The mercury-cistern was connected with a sensitive 

 electroscope. "When the platinum wire was electrified the 

 electroscope showed no trace of electricity. Thus the Torri- 

 cellian vacuum appeared here likewise to be a nonconductor 

 of electricity. Davy obtained the same result Avith a similar 

 experiment, in which two fine, very light threads were fixed 

 to a platinum wire soldered to the tube. When the electricity 

 was communicated to this, the fine threads diverged and main- 

 tained the divergence without modification, while if the va- 

 cuum had been a conductor they must have put themselves 

 into contact againf. E. Becquerel made a similar experiment, 

 which led to the same results %. 



Masson employed for his experiments the Torricellian 

 vacuum of a barometer in which the mercury had been care- 

 fully boiled §. Two platinum wires were soldered to the part 

 of the tube surrounding the vacuum. Masson tried in vain 

 to produce a discharge between these wares by means of a 

 Ruhmkorff induction-apparatus set in action by a powerful 

 battery; and he infers from this experiment that an absolute 

 vacuum must be considered an electric nonconductor. Some 

 very just remarks were made by Gaugain || in opposition to 

 the results of a more recent experimental, in which Masson 

 succeeded in passing the current of a powerful Euhmkortf 

 induction-apparatus through the Torricellian vacuum. 



Some mercurial vapour always remains in the Torricellian 

 space above the column of mercury ; it is therefore not an 

 absolute vacuum. To obtain a more complete one, Gassiot** 

 proceeded as follows : — Through a glass tube furnished with 

 platinum wires at its extremities, into which a certain quan- 

 tity of potass had been introduced, he passed a current of pure 

 carbonic acid until it could be assumed that all the air had 

 been expelled ; then the carbonic acid was rarefied by means 

 of an air-pump, and the tube was closed. Connecting now 

 the two platinum wires with the two poles of a powerful induc- 

 tion-apparatus, a continual transformation of the electrical 

 luminous appearance presented itself as the carbonic acid was 



* Gilbert's 'Annals,' xi. p. 164 ; Riess, Die Lehre von der Reibunys- 

 electricitdt, i. p. 39. 



t Phil. Trans. 1822; Rieas, /. c. p. 42. 



X Mascart, Traite de VSlectricite etatique, ii. p. 100. 



§ Ann. de Chim. et de Physique (8) xxxi. pp. 312-315. 

 Comi>tes Rendus, xli. p. 152. ^J Ibid, xxxvi, 



Mascart, Traite de Vclectricite statique, ii. p. 101. 



